This application claims the benefit of a Japanese Patent Application No.2000-205283 filed Jul. 6, 2000, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to replaceable units and apparatuses having replaceable units, and more particularly to a replaceable unit such as a fixing unit, and to an apparatus having such a replaceable unit.
An image forming apparatus such as an electrophotography type printer is provided with a replaceable unit which is periodically replaced depending on a serviceable life of the replaceable unit. A fixing unit is one example of such a replaceable unit. A replacement interval of the fixing unit is determined depending on the service time, that is, the time for which the fixing unit is used, and the fixing unit is replaced by a new fixing unit when the service time is exceeded.
2. Description of the Related Art
Conventionally, the replacement interval of the fixing unit of the image forming apparatus, such as a printer, copying machine and facsimile machine, is determined based on an operation time for which the fixing unit is driven or a number of prints made by the fixing unit. The operation time of the fixing unit or the number of prints made by the fixing unit is counted in a counter within the image forming apparatus, and is stored in a memory within the image forming apparatus. When a counted value in the counter exceeds a predetermined value, the replacement interval of the fixing unit is notified to the user by turning ON a lamp, for example. When replacing the fixing unit by a new fixing unit, the counted value stored in the memory is cleared.
On the other hand, it is necessary to judge whether the fixing unit is new or used. According to a conventional method of judging new and used fixing units, a fuse is provided on the fixing unit. This fuse is cut when starting to use the new fixing unit, so that the new and old fixing units can be distinguished from each other by detecting the state of the fuse. Such a method of judging the new and used fixing units is proposed in a Japanese Laid-Open Patent Application No.11-153918, for example.
Furthermore, another method of judging the new and used fixing units is proposed in a Japanese Laid-Open Patent Application No.11-288191, for example. According to this proposed method, a mechanical switch is provided on the fixing unit, and this mechanical switch is disconnected when the new fixing unit is driven.
However, the conventional methods of judging the new and used fixing units provide the fuse or the mechanical switch on the fixing unit, and cut or disconnect the fuse or the mechanical switch by supplying power to the fixing unit when starting to use the fixing unit. For this reason, there was a problem in that, when forwarding the fixing unit, it is impossible to confirm whether or not a function for judging the new and used fixing units correctly operates, because the fuse or the mechanical switch will be cut or disconnected when this function is tested, and the state of the fuse or the mechanical switch cannot be restored.
In addition, the replaceable unit may include a part which actually needs to be replaced and a part which may continue to be used. However, even in the case of the replaceable unit in which such parts coexist, the fuse or the mechanical switch will be cut or disconnected in the used replaceable unit. For this reason, even if the part which needs to be replaced is replaced by a new part in the used replaceable unit and this replaceable unit is placed in the image forming apparatus, this replaceable unit will be judged as being a used replaceable unit even though this replaceable unit should be regarded as being a new replaceable unit. Consequently, there was a problem in that the parts utilization efficiency of the conventional image forming apparatus and replaceable units is poor.
Accordingly, it is a general object of the present invention to provide a novel and useful replaceable unit and apparatus having a replaceable unit, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a replaceable unit and an apparatus having such a replaceable unit, which employ a relatively simple construction to enable correct judgement of new and used replaceable units even after a function for judging the new and used replaceable units is tested, and also enable correct judgement of new and used replaceable units even when a part of a used replaceable unit is replaced by a new part to be reused as a new replaceable unit, so that the parts utilization efficiency of the apparatus and replaceable units is improved.
Still another object of the present invention is to provide a replaceable unit to be placed in an apparatus, comprising a relay, including a latching type switch, outputting a new/used identification signal which indicates whether the replaceable unit is new or used depending on open and closed states of the switch, a detecting part detecting an operating state within the replaceable unit and outputting a state detection signal indicating the operating state, and a single signal line which is used in common for transferring the new/used identification signal and the state detection signal. According to the replaceable unit of the present invention, it is possible to employ a relatively simple construction to enable correct judgement of new and used replaceable units even after a function for judging the new and used replaceable units is tested, and also enable correct judgement of new and used replaceable units even when a part of a used replaceable unit is replaced by a new part to be reused as a new replaceable unit, so that the parts utilization efficiency of the apparatus and replaceable units is improved.
In the replaceable unit, the relay may switch the switch to an open or closed state to output a new/used identification signal which indicates that the replaceable unit is used, in response to a used setting signal which sets the replaceable unit as being used. In this case, the single signal line may further be used in common for transferring the used setting signal.
In the replaceable unit, the relay may further include a coil which is coupled in series to the switch, the detecting part may be coupled in parallel to the relay, and the single signal line may be coupled to a node which connects the relay and the detecting part. The replaceable unit may further comprise terminals, coupled to the relay, receiving a bias voltage for switching the switch to an open or closed state.
A further object of the present invention is to provide an apparatus having a replaceable unit, comprising a single signal line inputting a new/used identification signal which indicates whether the replaceable unit is new or used, and a state detection signal which indicates an operating state of the within the replaceable unit, and a controller detecting whether the replaceable unit is new or used based on the new/used identification signal which is input via the single signal line, and detecting the operating state within the replaceable unit based on the state detection signal. According to the apparatus of the present invention, it is possible to employ a relatively simple construction to enable correct judgement of new and used replaceable units even after a function for judging the new and used replaceable units is tested, and also enable correct judgement of new and used replaceable units even when a part of a used replaceable unit is replaced by a new part to be reused as a new replaceable unit, so that the parts utilization efficiency of the apparatus and replaceable units is improved.
In the apparatus, the controller may output a used setting signal which sets the replaceable unit as being used, and the single signal line may be used in common for outputting the used setting signal to the replaceable unit.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.